A silver halide photographic material (hereinafter referred to as a photographic film) has a basic structure comprising a silver halide emulsion layer provided on a support. In order to record information other than image in photography or printing, a conventional silver halide photographic material is provided with one or more magnetic recording layer in the form of a long stripe on an area other than the photographic image area of the material. However, the stripe part brings about occurrence of flex unevenness in the photographic film, or a deterioration of photographic characteristics caused by air trapped on a portion between the stripe parts.
U.S. Pat. Nos. 3,782,947 and 4,279,945 disclose a photographic film provided with a transparent magnetic recording layer on an image area. In the case of providing the magnetic recording layer to the image area, it is required to minimize a content of a ferromagnetic powder to prevent lowering of photographic sensitivity caused by adsorption of light by the ferromagnetic powder. Naturally, reduction of the content of the ferromagnetic powder decreases magnetic recording or reproducing characteristics. Accordingly, it is desired that the disadvantageous feature caused by the reduction of the amount of the ferromagnetic powder minimized.
In such photographic films with a magnetic recording layer, information is recorded and reproduced using a magnetic head. To increase the amount of information, track number of the magnetic head is generally designed to increase, while the increase of the track number generally makes one track to have a very narrow track width. If the dimension of the film is greatly apt to vary with change of temperatures or humidity, the recording location and the reproducing location are sometimes deviated to give error. Accordingly, it is desired that a support of the photographic film shows an excellent dimensional stability.
Further, in the case that a long continuous photographic film is incorporated into a cylindrical cartridge having certain dimension, or a continuous photographic film having a certain length is incorporated into a compact cylindrical cartridge, it is preferable that a thickness of a support of the film is as thin as possible. However, the thin support is apt to show a low mechanical strength (e.g., braking, bending), so that the support of such photographic film is preferably improved in its mechanical strength.
Cellulose triacetate, which is a conventional support material of a photographic film, does not satisfy characteristics such as an excellent dimensional stability and a high mechanical strength. The most adequate material satisfying the above characteristics, is polyester from the viewpoint of transparency and production cost. The abovementioned U.S. Pat. Nos. 3,782,947 and 4,279,945 disclose use of polyester as material of the support.
In more detail, photographic materials of the above patents are obtained by forming a magnetic recording layer comprising a magnetic powder and a binder of polyvinyl chloride and the like (i.e., polymer except polyester) on a polyester support. However, the recording layer does not sufficiently adhere to the support so that the recording layer sometimes separates from the support when it is run in contact with a magnetic head. Further, provision of the recording layer by a coating method using organic solvents brings about pollution of manufacturing environment due to the evaporated organic solvents. Furthermore, the use of a coating method is not advantageous from the viewpoint of productivity.
PCT International Publication No. W091/11750 discloses a photographic film which is prepared by simultaneously casting a cellulose triacetate solution and a cellulose triacetate solution containing a ferromagnetic powder on a cast surface and evaporating a solvent from the solution. This process does not need a coating process and hence it is advantageous in terms of productivity. However, since cellulose triacetate is used as the film material, the obtained photographic film does not have satisfactory characteristics such as dimensional stability and mechanical strength.